1. Field of the invention
The present invention concerns a press tool fitted with a system for guiding and relieving or disengaging a metal strip.
For the manufacture of thin metal or sheet metal pieces tools that are mounted upon a press or stamping machine are utilized to carry out punching, swaging, cambering, bending and similar operations. These tools are often so-called "picking-up tools" and "following-up tools". The term "picking-up tool" normally designates a press tool that operates only once on a metal sheet so as to confer thereupon a more or less complex form. Operations such as punching, swaging, bending, stamping, etc., generally cannot be performed by a single picking-up tool but require a range of such tools. The term "following-up tool" generally designates a tool comprising a plurality of aligned working stations, disposed one after the other, upon which a metal or sheet metal strip is caused to pass stepwise, at a determined rate, in order to carry out on this strip at each of these working stations, a preestablished operation such as punching, swaging, bending, stamping, etc. A finished piece is obtained at the exit from the last one of said working stations which is severed from said metal or sheet metal strip and presenting a more or less complex form.
These tools generally comprise stamps and dies, attachment parts such as blank-holders, punch-holders and die-holders, stay blocks and systems for guiding the metal or sheet metal strips in their step-by-step progression between the stamps and the dies.
According to a conventional technique, each stamping tool is designed so as to correspond to a given piece to be manufactured. This means that there exist as many tools as there are types of pieces to be manufactured. In fact, when using such tools, any modification of dimension and/or shape of a given work piece requires a complete change of the tool. This results in considerable expense in raw material, man-power and time.
According to another known technique, the dies and stamps of a following-up tool are detachable and interchangeable so that various pieces having different dimensions and shapes can be successively produced upon conveniently changing the dies and stamps. However, such a tool can be used only for a single width of metal strip and produces only pieces comprised within narrow dimensional limits of the width as well as the height of the piece. When pieces having relatively small dimensions are produced with such a tool from a single metal strip designed for pieces having relatively greater dimensions, this creates waste in the form of the resulting large amount of metal scrap. When such a tool is designed for manufacturing relatively flat pieces, it is not adapted to produce pieces subjected to bending which results in relatively bulky dimensions in height, since the metal is not sufficiently raised above the dies. The risk is also present that the piece will be blocked in its progression or become severely deformed.
It is an object of the present invention to overcome these drawbacks by providing an efficient, economic press tool fitted with an improved system for guiding and relieving or raising (i.e. disengaging) the metal strip, which allows the tool to be utilized with metal strips having different widths for successively manufacturing various pieces having different dimensions, as well as pieces having different heights, while achieving considerable savings in raw material, man-power and production time.
With this and other objects in view, the invention provides a press tool provided with a system for guiding and relieving a metal strip moving through the tool between dies and punches, which comprises a system for guiding and relieving the metal strip, which system includes sliding and interchangeable adjustable means, which are adapted to be adjusted and used for different preselected widths of metal strips and for varying degrees of brittleness of the metal strips used, as well as for different predetermined bulks of the upper parts of the pieces to be manufactured and for the various mechanical operations carried out by the tool.